Real-Time, Label-Free Detection of Nucleic Acid Amplification in Droplets Using Impedance Spectroscopy and using Solid-Phase Substrates

Tech ID: 25219 / UC Case 2012-202-2

Brief Description

Researchers at UC Irvine have developed a technology to detect the
presence of nucleic acid amplification in a droplet. This technology yields
real time detection of DNA or RNA amplication in a high throughput integrated
microfluidic platform.

Full Description

Polymerase
Chain Reaction (PCR) is a standard procedure used to amplify specific regions
of DNA or RNA across several orders of magnitude to generate thousands to
millions of copies pf a particular DNA or RNA sequence. Droplet microfluidics
represent an advance in this technology. Droplet microfluidics use droplets as
a platform for isolated reaction chambers. Detection of the generated
oligonucleotides typically involve using a fluorescence probe. This can be
costly and involves more post-processing steps.

Researchers
at UC Irvine have improved upon this system by developing a technology that uses
impedance-based detection that eliminates the need for fluorescently labelled.
The process is illustrated in Figure 1. When DNA or RNA is present within the
droplets, primers conjugated to the nanoparticles cause aggregation of the
nanoparticles during the PCR process (Fig. 1, right). This causes changes in
the electrical properties, which can be measured by subjecting the droplet to a
certain electrical field. The impedance measurements are used to determine the
presence of amplified DNA or RNA in the droplet.

Figure 2 shows the reference plots of peak-to-peak voltage data obatined
from measuring reference droplets from a variety of sizes at four frequencies. Each data point represents a single droplet. Linear fitting
of the collected peak-to-peak voltage data creates reference curves. The curves
show obvious differences in the voltage signals obtained from droplets
containing amplified DNA and non-amplified DNA. These reference curves can
subsequently be used as a predictor for DNA amplification in test droplets.

This technology
can be developed into a platform for detection of amplified DNA or RNA for
applications in droplet microfluidics. Figure 3 illustrates a platform that incorporates impedance-based detection method. The
device contains a thermocycling region for PCR, a set of detection electrodes,
and electrical contact pads. Test droplets flow over the detection electrode
through a fluidic channel in sequence. The detection electrodes are coupled
with a current amplifier and an impedance spectroscope which provide
measurement mechanism for electrical impedance of each droplet in the fluidic
channel.

Figure 3

Suggested uses

This technology can be used for real-time DNA/RNA detection at high
efficiency.

Advantages

This technology is able to discriminate precisely between samples that contain DNA and samples that contain amplified DNA. It is high-throughput and amenable with microfluidic technologies.